Why is seawater a better conductor of electricity than water from a freshwater lake?

1 Answer
Jun 12, 2017

Sea water is a better conductor because it has dissolved and dissociated ions.


The conductivity of water depends on the concentration of dissolved ions in solution.

The units of conductivity are Siemens per metre S/m.

Deionised water by its nature has very few ions. Its conductivity is about #5.5mu#S/m.

Sea water has a relatively large number of Sodium and Chloride ions and has a conductivity of around 5S/m. This is because the Sodium Chloride salt dissociates into ions.

Hence sea water is about a million times more conductive than fresh water.